feat(memory): improve oversized alloc handling & cleanup

Enhanced FreeList to handle oversized allocations by bypassing chunk management and allocating directly from the OS, with proper header assignment and immediate release on free. Updated IUnsafeCollection<T> documentation, removed unnecessary array clearing in Clear() methods, refined UnsafeSlotMap initialization logic, and removed redundant default element addition. Bumped assembly version to 1.5.1.

Misaki.HighPerformance.LowLevel/Buffer/FreeList.cs

@@ -540,10 +540,15 @@ public unsafe struct FreeList : IDisposable
                     ptr = TryPopFromBucket(cache, cacheIndex, bucketIndex);
                 }
             }
-
+            else
-            if (ptr == null)
             {
-                ptr = AllocateFromChunk(cacheIndex, totalSize, alignment);
+                // Oversized block: Bypass chunk linking entirely and go straight to the OS
+                ptr = AlignedAlloc(totalSize, alignment);
+                if (ptr != null)
+                {
+                    // Pass null for ownerChunk so 'Free' knows this is a standalone allocation
+                    AssignBlockHeader((BlockHeader*)ptr, null, totalSize, cacheIndex);
+                }
             }
 
             if (ptr == null)
@@ -604,10 +609,10 @@ public unsafe struct FreeList : IDisposable
 
         if (bucketIndex < 0)
         {
-            header->ownerChunk = null;
+            // This is an oversized allocation. It doesn't belong to a bucket or a chunk.
-            header->blockSize = 0;
+            // Erase the magic number for safety and instantly yield it back to the OS.
             header->magicNumber = 0;
-            header->ownerCacheIndex = 0;
+            AlignedFree(blockStartPtr);
             return;
         }
 

Misaki.HighPerformance.LowLevel/Collections/Contracts/IUnsafeCollection.cs

@@ -28,7 +28,7 @@ public interface IUnsafeCollection<T> : IUnsafeCollection, IEnumerable<T>
     where T : unmanaged
 {
     /// <summary>
-    /// Gets the number of elements in a collection. The value is read-only.
+    /// Gets the number of elements in a collection.
     /// </summary>
     int Count
     {

Misaki.HighPerformance.LowLevel/Collections/UnsafeList.cs

@@ -467,7 +467,6 @@ public unsafe struct UnsafeList<T> : IUnsafeCollection<T>
 
     public void Clear()
     {
-        _array.Clear();
         _count = 0;
     }
 

Misaki.HighPerformance.LowLevel/Collections/UnsafeQueue.cs

@@ -193,7 +193,6 @@ public unsafe struct UnsafeQueue<T> : IUnsafeCollection<T>
 
     public void Clear()
     {
-        _array.Clear();
         _count = 0;
         _offset = 0;
     }

Misaki.HighPerformance.LowLevel/Collections/UnsafeSlotMap.cs

@@ -132,8 +132,8 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
         if (!allocationOption.HasFlag(AllocationOption.Clear))
         {
             _generations.AsSpan().Clear();
+            _validBits.ClearAll();
         }
-        _validBits.ClearAll();
 
         _count = 0;
         _capacity = capacity;
@@ -324,8 +324,6 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
         _validBits.ClearAll();
 
         _count = 0;
-
-        Add(default, out _);
     }
 
     public readonly void* GetUnsafePtr()

Misaki.HighPerformance.LowLevel/Collections/UnsafeSparseSet.cs

@@ -396,8 +396,6 @@ public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
 
         _count = 0;
         _nextId = 0;
-
-        Add(default, out _);
     }
 
     /// <inheritdoc/>

Misaki.HighPerformance.LowLevel/Collections/UnsafeStack.cs

@@ -221,7 +221,6 @@ public unsafe struct UnsafeStack<T> : IUnsafeCollection<T>
 
     public void Clear()
     {
-        _array.Clear();
         _count = 0;
     }
 

Misaki.HighPerformance.LowLevel/Misaki.HighPerformance.LowLevel.csproj

@@ -7,7 +7,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <Authors>Misaki</Authors>
-    <AssemblyVersion>1.5.0</AssemblyVersion>
+    <AssemblyVersion>1.5.1</AssemblyVersion>
     <Version>$(AssemblyVersion)</Version>
     <PackageProjectUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</PackageProjectUrl>
     <RepositoryUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</RepositoryUrl>